Loud-speaker



F. MASSA 2,217,171

LOUD- S PEAKER Filed Oct. 50, 1931 I 2 Sheets-Sheet 1 Inventor attorney F. MASSA Oct. 8, 1940.

LOUD-SPEAKER Filed Oct. 30, 1937 2 Sheets-Sheet 2 I IV WWWk Gttonieg Patented Oct. 8, 1940 UNITED STA Es LOUD- SPEAKER Frank Massa, Audubon, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 30, 1937, Serial N0. 171,842

15 Claims.

This invention relates to loud-speakers of the dynamic type, and more particularly to means for maintaining the operating coils of such loudspeakers at as low a temperature as possible, the

5 principal object of this invention being to provide an improved loud-speaker having increased power rating.

More specifically, it is an object of my invention to provide means for facilitating the conduction of heat from the loud-speaker voice coil so that the temperature rise therein will be kept at a minimum.

Another object of my invention is to provide improved loud-speaker cooling means which can be applied to conventional loud-speakers.

Still another object of my invention is to provide an improved loud-speaker as aforesaid which is simple in construction and highly eflicient in use.

In accordance with my present invention, I provide a hermetically sealed structure within which the operating coils of the loud-speaker are housed and which is filled with a gas of high thermal conductivity. Means are also provided for suitably admitting such gas to the sealed housing, as is also means permitting a balance of pressure between the gas within said housing and the atmospheric pressure, whereby the average pressure within said housing will equal that of the atmosphere. This is necessary in order to maintain an equal pressure against each of the surfaces of the loud-speaker diaphragm at all times and to prevent appreciable static displacement of the loud-speaker diaphragm in an axial direction due to changes in atmospheric pressure. By filling the housing with a gas having high thermal conductivity, the heat generated in the loud-speaker coils will be conducted more easily to the radiating surfaces of the housing, thus making it possible to increase the power rating of the loud-speaker. Also, the temperature rise of the voice coil of the loud-speaker will be greatly reduced if a highly thermal conductive gas is used as the conducting medium in the magnetic gap in which the voice coil operates.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. However, the invention itself, both as to its organization and method of operation, together with additional objects and advantages thereof, will best be understood from the following description of several embodiments thereof, when read in connection with the accompanying drawings, in which Figure 1 is a plan view, partly broken away,

of one form of loud-speaker according to my present invention,

Figure 2 is a sectional View thereof taken on the plane of the line IIII of Fig. 1,

Figure 3 is a central sectional View of one form 5 of valve mechanism suitable for admitting the highly heat conductive gas to the loud-speaker housing and for permitting withdrawal of the air from the housing,

Figure 4 is a view similar to Fig. 2 of another 10 embodiment of my invention,

Figure 5 is a similar view showing a modified form of the housing shown in Fig. 2, and

Figures 6, '7 and 8 are curves showing temperature rises in the voice coils of loud-speakers 15 according to my invention as compared with conventional speakers operating in air.

Referring more particularly to the drawings, wherein similar reference characters designate corresponding parts throughout, I have shown, in 20 Figs. 1 and 2, a loud-speaker comprising a substantially cylindrical magnetic yoke I open only at the top and having the usual core, or center pole piece 3 thereon around which is fitted a field coil 5. Hermetically sealed to the yoke I is a magnetic yoke plate I provided with a plurality of openings 9 and adapted to cooperate with the core 3 to provide an air gap II therebetween. In turn, hermetically sealed to the yoke plate I is an annular member I3 which is adapt- 30 ed to support a cone or diaphragm I5 of nonporous material, such as aluminum, the cone I5 being itself hermetically sealed to the support I3 in any suitable manner. The assembly thus far described constitutes an air-tight housing 3 within which are located the field coil 5 and a voice coil Il carried by the diaphragm I5 for operation in the magnetic gap I I.

The field coil leads I8 and the voice leads 20 are brought out through insulated bushings 22 for external connection. Tapped in the housing assembly previously described are a pair of openings into which may be threaded suitable valve devices for admitting into the space bounded by the yoke I, the annular member I 3 and the 45 diaphragm I5 a highly thermal conductive gas, such as hydrogen or helium. One of the openings, for example, the opening I9, may be formed in the yoke I, and the other opening 2| may be formed in the annular member I3, if desired. Into each of the openings I9 and H is threaded a valve device constituted by a bored member 23 having a conical seat 25. A second member 21, which is also centrally bored, terminates in a conical tip 29 from which a plurality of ducts 3I 55 lead to the central bore of the member 21, the member 21 being threaded in the bore of the member 23. In the position shown in Fig. 3, communication is established between the atmosphere and the interior of the housing assembly. Thus, in this position, it is possible to admit the highly thermal conductive gas through one of the valves, preferably that in the opening 2|, and at the same time to withdraw the air originally within the housing assembly through the other valve, namely, that in the opening I9. After the space within the housing assembly has been filled with suitable gas (which is made possible by reason of the openings 9 in the yoke plate 1) the elements 2! may be tightened until their conical tips 29 will seat against the conical seats 25, whereupon a tight seal will result. Thereupon, both valves may be hermetically sealed, if desired.

Within the wall of either the yoke I or the annular member I3 there is provided an opening 33 into which may be fitted another valve device 35 provided with a flexible member 31, such as a phosphor-bronze bellows or other suitable resilient membrane. The resilient member 31 should be large enough to be readily responsive to changes in atmospheric pressure, so that the pressure of the gas in the housing assembly may at all times be equal to the atmospheric pressure. This is necessary in order to provide equal pressure on each of the radiating surfaces of the cone I5.

When the space within the housing assembly heretofore described is completely filled with hydrogen, helium, or other suitable gas, it has a high thermal conductivity, and the heat generated in the voice coil I! and in the field coil 5 will be conducted away with much greater ease than if this space were filled with air. Hydrogen has a thermal conductivity 7 .1 times that of air, and helium has a thermal conductivity 6.25 times that of air. It will, therefore, be readily apparent that the heat can be conducted away from the coils 5 and II much more efiiciently when using a gas of the type referred to above, instead of air. By conducting the heat away from the voice coil II more eificiently, the temperature rise in the voice coil, for a given power output, will be greatly lowered, thus permitting an increase in rating of the loud-speaker. If desired, the heat which is conducted from the coils 5 and II to the iron or similar yoke I by the gas within the housing assembly may be caused to become dissipated into the atmosphere more rapidly than in conventional loud-speakers. For this purpose, the yoke I may be provided with a series of external fins 39, as shown in Fig. 5.

In order to impart to conventional loud-speakers now in use the benefits of my invention, without materially altering their structures, a housing M of iron or the like may be provided, as shown in Fig. 4. The housing M is fitted with the valve devices 23-2'i, as in the modification of Fig. 1, and it is also provided with the valve device 35. Preferably, also, the housing M is formed with a plurality of heat dissipating fins 39, as in the modification shown in Fig. 5.

The housing ii is open only at the top and is formed with an inwardly extending fiange 43 to which the cone housing support 45 may be hermetically sealed, the cone I5 being hermetically sealed to the support 45 as in the case of the modification shown in Figs. 1 and 2. The yoke I and its core 3, as well as the yoke plate I, may be similar to that herefore described. Preferably, a bracket 41 of copper or other highly thermal conductive metal is secured to the housing ll and to the yoke I for rapidly conducting away ,to the housing 4| the heat generated in the coils 5 and I1 and transferred thereto by the highly thermal conductive gas within the housing II. A valve device 35 similar to that shown in Fig. 1 may also be provided in the housing 4|.

In Figs. 6, '7 and 8 are shown curves from which a comparison of the temperature rise in the voice coil may be obtained when using air in one case and helium in the other. The curve shown in Fig. 6 is for a small loud-speaker with a D. C. input to the voice coil II. It will be noted that the temperature rise, where the voice coil is surrounded by helium, is considerably less than that of a similar voice coil immersed in air, and that the slope of the helium curve is much smaller than that of the air curve.

Fig. '7 shows the curves for a high powered loud-speaker with a D. C. input to the voice coil.

The same conclusions may be drawn as from the curves in Fig. 6.

Fig. 8 is a set of curves applying to the same loud-speaker as that to which Fig. 6 applies, but with a lODO-cycle input to the voice coil. Here, again, the helium curve shows that the temperature rise in the voice coil is much less, for a given input, than in the case of air.

Although I have shown and described several embodiments of my invention, I am fully aware that many other modifications thereof are possible, and I desire, therefore, that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.-

I claim as my invention:

1. In electrical signal translating apparatus of the dynamic type, the combination of an hermetically sealed housing filled with a fixed quantity of gas of high thermal conductivity, at least one operating coil in said housing, and means carried by said housing responsive to changes in atmospheric pressure for maintaining the pressure of the gas within said housing at atmospheric pressure.

2. In an electrodynamic loud-speaker, the combination of a housing having an opening therein, a sound translating diaphragm closing said opening and hermetically sealed to said housing, an operating coil within said housing, and a gas of high thermal conductivity filling the space within said housing.

3. In an electrodynamic loud-speaker, the combination of a housing having an opening therein, a sound translating diaphragm closing said opening and hermetically sealed to said housing, a voice coil carried by said diaphragm within said housing, and a gas of high thermal conductivity filling the space within said housing.

4. The invention set forth in claim 3 characterized by the addition of means on said housing for admitting said gas and means also on said housing constituting an outlet for air originally within said housing.

5. The invention set forth in claim 3 characterized in that said housing is provided with a second opening and characterized further in that said second opening is'hermetically sealed by a flexible member readily responsive to changes in atmospheric pressure for maintaining the gas pressure within said housing at atmospheric pressure.

6. The invention set forth in claim 3 characterized in that said gas is constituted by hydrogen.

'7. The invention set forth in claim 3 characterized in that said gas is constituted by helium.

8. In an electrodynamic loud-speaker, the combination of a yoke of heat conductive material, a yoke plate carried thereby, a diaphragm support carried by said yoke plate, a diaphragm mounted on said support, said yoke, yoke plate, support and diaphragm being so connected as to provide an hermetically sealed housing as sembly, a voice coil carried by said diaphragm within said assembly, and a gas of high thermal conductivity filling said housing assembly.

9. The invention set forth in claim 8 characterized in that said yoke is provided with a plurality of elements on its outer surface for relatively rapidly dissipating the heat transferred thereto by said gas.

10. The invention set forth in claim 8 characterized by the addition of a plurality of valve devices in said housing assembly adapted to provide communication between the interior of said assembly and the exterior thereof.

11. The invention set forth in claim 8 characterized in that said housing assembly is provided with an opening, and characterized further in that said opening is covered by a flexible element readily responsive to changes in atmospheric pressure for maintaining the pressure of the gas within said housing assembly at. atmospheric pressure.

12. The invention set forth in claim 8 characterized in that said gas is constituted by hydrogen.

13. The invention set forth in claim 8 characterized in that said gas is constituted by helium.

14. In an electrodynamic loud-speaker, the combination of a yoke of heat conducting, magnetic material having a center pole piece thereon, said yoke being open at only one end, a magnetic yoke plate hermetically sealed to said yoke at said end and cooperating with said center pole piece to provide a magnetic gap therebetween, an annular member hermetically sealed to said yoke plate and constituting a diaphragm support, a metallic diaphragm hermetically sealed to said annular member, said diaphragm carrying a voice coil within said magnetic gap, and a gas of high thermal conductivity filling the space bounded by said yoke, said annular member and said diaphragm.

15. In an electrodynamic loud-speaker, the

combination of a yoke of heat conducting, magnetic material having a center pole piece thereon, said yoke being open at only one end, a magnetic yoke plate hermetically sealed to said yoke at said end and cooperating with said center pole piece to provide a magnetic gap therebetween, an annular member hermetically sealed to said yoke plate and constituting a diaphragm support, a metallic diaphragm hermetically sealed to said annular member, said diaphragm carrying a voice coil within said magnetic gap, a gas of high thermal conductivity filling the space bounded by said yoke, said annular member and said diaphragm, a plurality of valve devices adapted to provide communication between said space and the atmosphere, and means for maintaining the pressure of the gas within said space at atmospheric pressure.

FRANK MASSA. 

